The objective of this research is to prevent neurological damage from secondary cerebral ischemia, by identifying and treating reductions in cerebral blood flow (CBF) early, prior to development of irreversible damage. To achieve this goal, an on-line continuous monitor of cerebral oxygenation, using a fiberoptic oxygen saturation catheter positioned in the jugular bulb is being developed for use in neurologically injured patients. Preliminary data has been obtained to document the reliability of jugular venous oxygen saturation (SjvO2) as an estimate of CBF. Each episode of decreased SjvO2, detected by the continuous monitoring, will be confirmed by measurements of oxygen saturation in a blood sample drawn from the jugular catheter. The cause of each confirmed episode of decreased Sjv)2 will be investigated by a standard protocol and treated appropriately. Each episode of reduced CBF will be treated by a standard protocol that will permit the comparison of hypervolemic hemodilution, and low dose dopamine as the initial therapeutic modality. It is anticipated that development of arterial hypoxia, anemia, and cerebral ischemia will be identified and treated earlier with continuous monitoring of SjvO2 than would have been possible with standard monitoring of ICP and neurological examination.